1. Field of the Invention
The present invention relates to a novel disk rotating mechanism. More specifically, it relates to a technique for reducing the number of parts and achieving an improvement in assembly operability in a disk rotating mechanism equipped with a so-called automatic aligning mechanism in which oscillation with the rotation of the disk is cancelled even if there is unbalance in the disk weight by causing a balance member to move in a movement space.
2. Description of the Related Art
In a disk drive device provided, for example, in a computer and adapted to perform recording and reproduction to and from a recording disk such as an optical disk or a magneto-optical disk, the recording disk is rotated by a disk rotating mechanism. This disk rotating mechanism has a spindle motor serving as a rotating means and a turntable fastened to the forward end of the spindle shaft of the spindle motor and holding the central portion of the recording disk. With respect to the recording disk rotated by this rotating mechanism, the recording and/or reproduction of information signals is performed by an optical pick-up, a magnetic head device or the like.
The recording disk consisting of an optical disk or the like may be unbalanced in weight from production, etc. When a recording disk having such unbalance in weight is rotated by the disk rotating mechanism, the recording disk will oscillate with the turntable because the center of rotation does not coincide with the center of gravity. Due to this oscillation, the focusing and tracking on the signal recording surface of the recording disk by the optical pick-up device and the following of the recording track of the recording disk by the magnetic head device cannot be performed in a satisfactory manner.
In view of this, there has been proposed a rotating mechanism having an automatic aligning function in which a plurality of balance members are movably arranged in a movement space rotated by a rotating means and in which the balance members are rotated by the rotating means and move in the movement space so that the center of gravity (composite center of gravity) of the members rotated by the rotating means and rotating members contained in the rotating means (hereinafter these rotating members will be referred to as a "composite rotating body") is situated in the rotation axis. Examples of this rotating mechanism are shown in Japanese Patent Applications No. 9-53704, 9-96231, 9-96232, 9-96233, etc., filed by the present applicant.
FIG. 1 shows a conventional example of a disk rotating mechanism equipped with an automatic aligning mechanism.
As shown in FIG. 1, a disk rotating mechanism a comprises spindle motor b, a support shaft (spindle shaft) c rotated by the spindle motor b, an automatic aligning mechanism d arranged near the upper end of the spindle shaft c, and a turntable e secured to the upper end portion of the spindle shaft c.
The spindle shaft c is rotatably supported through the intermediation of rotary bearings h with respect to a shaft support member g supported by a mechanical chassis f. A rotor case i constituting the spindle motor b is attached to the spindle shaft c, and the rotor case i is substantially formed as a cylinder with one end surface closed, a cylindrical drive magnet j being secured to the inner peripheral portion thereof.
A stator coil k is attached to the shaft support member g, and the stator coil k is arranged so as to be opposed to the drive magnet j.
A motor substrate 1 is provided on the mechanical chassis f, and the motor substrate l supplies electricity to the stator coil k attached to the shaft support member g.
In the spindle motor b, when drive current is supplied to the stator coil k, a magnetic field generated by the stator coil k acts on the drive magnet j, and the drive magnet j and the rotor case i are rotated with the spindle shaft c, whereby the automatic aligning mechanism d and the turntable e are rotated integrally. That is, the spindle shaft c serves as the support shaft (drive shaft) of the spindle motor b.
The turntable e comprises a centering guide portion o into which the spindle shaft c is forced and at the central portion of which a protrusion n for positioning a recording disk is formed, and a disc-like table portion p protruding from the centering guide portion o in the direction perpendicular to the axis. The centering guide portion o is formed of a synthetic resin material, and the table portion p is formed of a non-magnetic metal material, the table portion p and the centering guide portion o being formed integrally by insert molding.
The positioning protrusion n protrudes in the form of a truncated cone, and is fitted into a central hole q of the recording disk m to perform the positioning of the recording disk m. Further, a magnet r is contained in the positioning protrusion n, and attracts a chucking member (clamper member) (not shown) including a magnetic material.
An annular friction sheet s is attached to the outer peripheral edge of the table portion p, and torque can be correctly transmitted to the recording disk m placed on the table portion p.
The automatic aligning mechanism d comprises a flat cylindrical case body t formed of a non-magnetic metal material and having one end surface closed, a ring-like attraction magnet u arranged in the case body t so as to be coaxial therewith, a plurality of balance members v accommodated in the space (movement space) between the attraction magnet t and the outer peripheral wall of the case body t, and an annular yoke w attached to the attraction magnet u.
The case body t is secured to the spindle c such that the closed end surface thereof is in contact with the closed end surface of the rotor case i, whereby the turntable e side end surface of the case body t is open.
Further, the open end surface of the case body t is covered with the table portion p of the turntable e. In the disk rotating mechanism a equipped with this automatic aligning mechanism d, when a predetermined number of revolutions is attained, the balance members v are detached from the attraction magnet u and come into contact with the inner surface of the outer peripheral wall of the case body t, and the balance members v move such that the mass eccentricity of the composite rotating body is canceled, whereby alignment is effected.
However, in the above-described conventional disk rotating mechanism a, the table portion p of the turntable e is made of a metal material, and is formed integrally with the centering guide o by insert molding, so that the number of parts is large. Further, due to the insert molding, the assembly operability is rather poor, with the result that the production cost is high.